Course Notes - Department of Mathematics and Statistics

Multiple linear regression prediction• We can predict the TLC for someone given their height and agenow. For example, if we had someone who was 25 years old and160 cm.ŷ = −11.1565 − 0.0300age + 0.1084heightŷ = −11.1565 − 0.0300 × 25 + 0.1084 × 160ŷ = 5.3757Including binary predictor variables• The predictor variable SEX, has two categories (males and females)• We need a technique for including these binary variables in theregression models.• We will use a dummy variable.Dummy variables• A dummy variable is defined to take the value of 0 for one of thecategories and 1 for the other category.• For our total lung capacity example we will set{0 if femaled =1 if male• If there are two other predictors X 1 and X 2 then the fitted equationis then.ŷ = ˆβ 0 + ˆβ 1 x 1 + ˆβ 2 x 2 + ˆβ 3 d234